Bradley Manning, the former Army private behind the biggest leak of classified information in recent history, went before a court-martial on Monday to face charges of espionage and treason.
Much of the information included classified State Department cables between Washington and various diplomatic outposts.
However, Manning also handed over a video showing American attack helicopters open fire on foreign journalists in Iraq when the news crew was mistaken for group of insurgents.
As a result of the leaks, he faces 22 counts of aiding the enemy and violations of the Espionage Act, which could send the former Army intelligence analyst to federal prison for life.
Military prosecutors opened Monday's hearing at Fort Meade, Md., by laying out the various charges Manning faces, according to reports.
Manning has admitted to handing over the classified information to WikiLeaks in an attempt to spark public debate on U.S. actions in Iraq and around the world.
The Manning court-martial is the culmination of nearly three years of pretrial hearings and motions, where both sides argued over what classified information can be allowed into trial.
Similar legal battled have plagued the ongoing military tribunal at Guantanamo Bay, Cuba, where Khalid Sheikh Mohammed and the four other 9/11 co-conspirators face terrorism charges.
Like the detainees in Cuba, Manning has been in held in military custody since his arrest in 2010.
Civil rights activists claim Manning had been subjected to cruel and unusual punishment during his incarceration.
Military guards reportedly held Manning in isolation for long periods and confiscated his clothing and other personal items during his detention.
Meanwhile, the Obama administration is under increasing political pressure over its prosecution of classified information leaks.
Congressional lawmakers are turning up the heat on Attorney General Eric HolderEric H. HolderTrust Women opposes Sen. Session's nomination Former AG launches redistricting effort to help Dems reclaim power The racism inquisition over Jeff Sessions MORE over concerns that the Justice Department violated the First Amendment rights of Associated Press and Fox News employees by seizing their telephone and email records in a pair of separate investigations into national security leaks.
The department came under fire last week after it was revealed that it secretly subpoenaed the phone records of more than 20 reporters and editors with the AP as part of a criminal investigation by the U.S. attorney for the District of Columbia into the release of information from a government official to the media.
Holder testified before the House Judiciary Committee in May that he recused himself from the case because he was interviewed by investigators as someone with access to the secret information in question and a possible source of the leak.